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Winds to ease, but here comes the freeze

It's time to cover those tomatoes and petunias. After howling to more than 40 mph at times today, winds will fall silent tonight and temperatures across the Northland are expected to plunge near and even well below the freezing mark, depending on...

It's time to cover those tomatoes and petunias.

After howling to more than 40 mph at times today, winds will fall silent tonight and temperatures across the Northland are expected to plunge near and even well below the freezing mark, depending on the area.

The first hard killing frost of the season is expected across most of Northeastern Minnesota on Wednesday morning, north of U.S. Highway 2 and away from Lake Superior.

Areas to the south of Highway 2 and near Lake Superior, including outlying areas near Duluth and Superior, could see a lighter frost.

Anyone in those areas with plants or vegetables should bring them in or cover them or they may perish, the National Weather Service in Duluth warns.

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Temperatures next to Lake Superior and very close to inland lakes should stay above freezing by a degree or two. That warmer air near lakes could cause some freezing fog on roadways early Wednesday, the Weather Service warns.

Tom Kasper, Duluth city gardener, said covering plants will help protect them down to 30 degrees, and even 28 degrees for some more hardy varieties.

"It acts as just enough insulation so the heat radiating up from the ground will keep them from freezing,'' Kasper said. "And it keeps the frost from physically touching and damaging the plant tissue, which is actually what can kill the plant.''

It's unusually early for such a deep pool of cold air to plunge into the Northland.

If frost hits Duluth, it will be 10 days before usual. And areas of the Arrowhead hit by a hard freeze will be about two weeks ahead of schedule.

Between 1948 and 2005 the median date for a frost -- temperatures of 32 degrees -- at Duluth International Airport was Sept. 23, according to data from the Minnesota State Climatologists Office. The average date for a hard freeze at the airport is Oct. 15.

The median date (half before, half after) for a first frost in International Falls is Sept. 15 and Sept 27 for a hard freeze.

Folks in the Cook, Embarrass and Tower areas will be about on schedule for their first killing frost.

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Cook, which has the shortest growing season of major reporting stations in Minnesota, usually sees a 32 degree low by Sept 10. That's only about 97 days, on average, from the median last frost on June 4 and gives Cook the shortest growing season in Minnesota.

Conditions are expected to improve for the rest of the week with low temperatures each morning mostly in 30s and 40s -- although there's a chance for some wet snow flurries mixed with rain on Thursday night north of the Iron Range.

John Myers reports on the outdoors, natural resources and the environment for the Duluth News Tribune. You can reach him at jmyers@duluthnews.com.
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